While visiting the sick Montag, Beatty explains (from a more knowledgeable perspective than most citizens) some of the things that caused the government to ban books. People were not happy, he explains; they had too many conflicting opinions from too many dissenting sources. People could not agree on things and so society was contentious and inefficient. Once the government figured out how to control the citizenry through TV and radio, it was simple to alter their consumption, focusing on emotion rather than reason.
"Give the people contests they win by remembering the words to more popular songs or the names of state capitals or how much corn Iowa grew last year. Cram them full of non-combustible data, chock them so damned full of 'facts' they feel stuffed, but absolutely 'brilliant' with information. Then they'll feel they're thinking, they'll get a sense of motion without moving."
(Bradbury, Fahrenheit 451, hrsbstaff.ednet.ns.ca)
In other words, make people obsessed with useless trivia instead of individual thought. People tend to go along with trends; when TV shows focus on useless things instead of education or real news, people will go along to impress their friends, all of whom assume that everyone else is following. As books with differing opinions become more scarce, people turn to TV and so become more like their neighbors; with time, people share all their opinions and ideas, all based on TV programming.